1. Field of the Invention
The present invention relates to a quick hardening cement-asphalt composition used for making a grout for a ballast-filled track structure.
2. Description of the Prior Art
A conventional ballast-filled track structure requires great labor or effort for safely maintaining the track structure after construction, such as, for example, tamping, the correction of the distortion of the track, and the renewal of the ballast and thus the development of a maintenence-free track structure has been keenly desired.
As countermeasures, a slab-type track structure, that is, a track structure wherein the spaces between the track slab and the base layer is filled with an elastic material and a ballast-filled track structure, that is, a track structure wherein the spaces between the ballast for a conventional ballast track structure are filled with an elastic material are known. The slab-type track structure has already been utilized in various applications such as new high speed railways such as the Shinkansen (Tokaido-Line), Japan and conventional railways, while for the ballast-filled track structure, a mixture of cement and asphalt has been employed as the elastic material.
However, since a ballast-filled track structure is applied to tracks on which trains have actually run, it is difficult to construct a ballast-filled track structure within a sufficient period of time. Therefore, the elastic material must be poured in the spaces between the ballast in a short period of time. Thus, the use of a cement-asphalt grout composed of a simple mixture of portland cement and asphalt is accompanied by the disadvantage that the grout does not exhibit the desired strength before the passage of a train after applying the grout to the ballast and hence the track is forced out of alignment considerably.
Therefore, attempts have been made to employ a cement-asphalt grout in which a commercially available quick hardening cemment is used as disclosed in U.S. Pat. No. 3,628,973 but such a cement-asphalt grout does not provide sufficient strength in a short period of time and this type of grout is unsatisfactory.
That is, the grout used for a ballast-filled track structure must have the following properties:
(1) the grout must exhibit a compressive strength above about 4 Kg/cm.sup.2 within about 60 to 90 minutes after execution,
(2) the consistency of the grout must be about 5 to 10 seconds with a J funnel (the PC grout test method by the Civil Engineering Society of Japan),
(3) the grout must maintain its consistency of item (2) above for at least 20 minutes after mixing, and
(4) the grout must exhibit the compressive strength of item (1) above at temperatures ranging from about 5.degree. to 35.degree. C.